Diphtheria

Aka: Diphtheria, Pseudomembranous Pharyngitis, Corynebacterium diphtheriae

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II. Epidemiology

  1. Rare in United States due to Immunization (DTP, DTaP)
    1. However 20% of adults may be inadequate Immune Status
  2. Ongoing epidemic in the former USSR

III. Pathophysiology

  1. Causative Organisms
    1. Corynebacterium diphtheriae is a non-spore forming Gram Positive Rod
    2. Other Corynebacterium species (ulcerans, pseudotuberculosis) may be rarely transmitted from animals to humans
  2. Diphtheria Toxin (Bacteriophage encoded, not carried by some strains of C. Diphtheriae)
    1. B-Binding Subunit
      1. Binds heart cells and Neurons
    2. A-Action Subunit
      1. Inactivates Elongation factor (EF2) via ADP ribosylation
      2. Inhibits mRNA translation into Proteins

IV. Symptoms

  1. Sore Throat
  2. Dysphagia
  3. Weakness
  4. Malaise

V. Signs

  1. Toxic appearance
  2. Low grade fever
  3. Tachycardia (out of proportion to fever)
  4. Pharyngeal erythema
  5. Gray-white tenacious exudate or "pseudomembrane" adheres to posterior pharynx
    1. Composed of white cells, Fibrin, necrosed epithelial cells and Diphtheria cells
    2. Nidus of infection, source of Diphtheria neurotoxic and cardiotoxic exotoxin which is absorbed systemically
    3. Occurs at Tonsillar Pillars and posterior pharynx
    4. Leaves focal hemorrhagic raw surface when removed
  6. Cervical Lymphadenopathy

VI. Differential Diagnosis

  1. Vincent's Angina (Trench Mouth)
    1. Also shows pseudomembrane formation
  2. Pharyngitis

VII. Labs

  1. Complete Blood Count (CBC)
    1. Leukocytosis
  2. Throat Culture and nasal culture
    1. Positive for Corynebacterium organisms (but results are typically delayed for days)
    2. Samples are plated
      1. Potassium tellurite agar
        1. Corynebacterium diphtheriae colonies become gray-black in the first day)
      2. Loeffler's Coagulated Blood Serum Media
        1. Sample incubated for 12 hours, then evaluated under methylene blue stain for Gram Negative Rods
    3. Further organism identification is via several methods including PCR, and specific toxin testing
      1. Not all C. diptheriae strains express Bacteriophage encoded toxin production

VIII. Management

  1. Droplet precautions
  2. Empiric treatment in suspected cases (do NOT delay treatment until culture confirmation)
  3. Diphtheria antitoxin (Equine serum from CDC)
    1. Scratch test before use
    2. Inactivates circulating toxin before it damages heart and nerve tissue
  4. Antibiotics for 14 day duration
    1. Erythromycin 20 mg/kg/day divided every 6 hours IV or
    2. Penicillin G 50,000 units/kg up to 1.2 MU/day IV every 12 hours, then transition to Penicillin VK when able
  5. Culture and Treat contacts
    1. Procaine Penicillin for 1 dose OR
    2. Erythromycin for 7-10 days

IX. Prognosis

  1. Without treatment, Diphtheria has a mortality rate as high as 50%
  2. With treatment, mortality may still approach 5-10%

X. Prevention

  1. DTP Vaccination or DTaP Vaccination
    1. Also administer to recovered patients (infection does not ensure Immunity)

XI. Resources

  1. CDC - Diphtheria
    1. https://www.cdc.gov/diphtheria/clinicians.html

XII. References

  1. Sanford Guide, accessed on IOS 12/29/2019

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